ALBERT

Notes: Summary ThepO2 in the hemolymph of the decapod crustaceanAstacus leptodactylus was measured continuously with micro O2 electrodes. PostbranchialpO2, heart rate and ventilation rate were simultaneously recorded. PrebranchialpO2 was measured in a separate series of experiments. Crayfish acclimated for six weeks to warm (20 °C) and cold (10 °C) conditions were studied. 1. Postbranchial bloodpO2 was measured in the pericardium. Typical values for warm-acclimated animals fell in the range 23–35 Torr, with a mean of 28.3 Torr, and those for cold-acclimated animals were 17–30 Torr, with a mean of 24.4 Torr. PrebranchialpO2 was measured in the meropodites of the 8th thoracopod. VenouspO2 levels ranged from 7–13 Torr, mean 9.4 Torr (warm-acclimated), and 6–9 Torr, mean 6.8 Torr (cold-acclimated). 2. pO2 values of resting, restrained animals were variable and fluctuations occurred in both the pre- and the postbranchial levels. Fluctuations were either small (1–5 Torr) or large (10–70 Torr). 3. PostbranchialpO2 correlated with fluctuations in the ventilation and heart rates. ArterialpO2 rose when the ventilation rate was increased, with a delay of about 10 s in warm-acclimated and 20 s in cold-acclimated animals, respectively. Along with increasingp aO2 an increase of the heart rate was established. 4. In resting animals, there is no a-v pH-difference. Cell-free hemolymph, taken from the pericardium or the meropodites, had a pH of 7.48 or 7.47, respectively, in warm-acclimated animals and 7.94 or 7.97 in cold-acclimated animals. Under these conditions the hemocyanin was 99% saturated in the artial blood and 45% in venous (warm-acclimated). Corresponding values in cold-acclimated crayfish were 98% and 61%, respectively. 5. TheP 50 of the hemocyanin in undiluted hemolymph was 10 Torr at 20 °C and pH 7.42, and 6.2 Torr at 10 °C and pH 7.92. The hemocyanin showed a weak Bohr effect (ΔlogP 50/ΔpH=−0.19 in warm-acclimated, and −0.20 in cold-acclimated animals). The pH range of the Bohr effect fell into the in vivo pH range in each group and thus differed by 0.5 pH units between the two groups.

Notes: Summary pO2 and pH were continuously recorded by microelectrodes in hemolymph of the spiderEurypelma californicum before, during and after locomotor activity. ArterialpO2 values were obtained in the heart, and venouspO2 in the ventral sinus of the prosoma and in the coxa of the fourth walking leg. pH was recorded in the heart and in the ventral sinus. 1. In resting animals thepO2 was very low (p aO2: 28 Torr,p vO2: 16 Torr (ventral lacuna) and 14.4 Torr (coxa)). Most animals exhibited intermittent fluctuations in oxygen pressure, with amplitudes between 1 and 10 Torr. 2. During activity the oxygen pressure in the heart remained almost unchanged, whereas venouspO2 began to fall soon after the spider began to walk. Oxygen pressure in the coxa sometimes fell to zero, but the blood in the ventral sinus was never completely deoxygenated. 3. When the spider had stopped walking thepO2 increased to a new, higher level at all three sites, reaching at the end of recovery phase an average of 74.2 Torr in the heart, 24.8 Torr in the ventral sinus and 24 Torr in the coxa. If the animals then became active at these highpO2 levels, much smaller transient decreases occurred in the arterial and venous O2 pressures. The highpO2 level was usually maintained for 15–25 min; then, if no further activity occurred, it fell rapidly. 4. Resting heart rates were between 30 and 40 min−1, and independent of hemolymphpO2. Immediately after stimulation, the heart rate showed little change, but it increased thereafter. After activity, when oxygen pressure was high, heart rate andpO2 were negatively correlated. 5. Resting pH averaged 7.49 in the heart and 7.45 in the ventral lacuna. After activity, pH in the heart fell by as much as 0.25 unit, and in the ventral sinus by as much as 0.5 unit. The observed changes in pH following activity depended upon the length of the preceding rest period; long periods of rest were associated with a single pH minimum, but if repeated bursts of activity had occurred two pH minima were recorded. 6. In diluted (1∶20) hemolymph theP 50 of the hemocyanin (Hcy) is 27.8 Torr at 23°C and physiological pH (7.5). ΔlogP 50/ΔpH amounts to −0.56 at 23 °C and pH 6.9–8.4. The Hill coefficient,n H, is 7 at pH 7.5 and 3.5 at pH 7.25. It is calculated that the Hcy of resting animals is only 52% saturated in the arterial blood, and 5% saturated in the venous blood. After activity, at highp aO2, the hemocyanin becomes completely saturated.

Notes: Summary By means of Pt-microelectrodes, oxygen pressure was measured in the haemolymph and in various tissues of the tarantula,Eurypelma helluo. 1. In resting, restrained animals, the arterialpO2 obtained in the heart is 31 Torr. The venouspO2 in haemolymph of the thir femur is 9.7 Torr. The same pressure was found in the haemolymph of the metatarsus. 2. Tissue oxygen pressures were measured in the dorsal region of the opisthosoma (comprising gut diverticula, pericardium, and heart), in the head region of the prosoma, and in the femur. The oxygen profiles obtained by advancing the electrode in 20–40 μ increments are reproducible and characteristic of each region. Inside the muscles the lowest pressures were 1–3 Torr (heart wall), 4–10 Torr (muscles of the prosoma), and 1–4 Torr (femur muscle). ThepO2 gradient between haemolymph and tissues is approximately 13 Torr/100 μ in the heart wall, 7 Torr/100 μ in muscles of the prosoma, and 3 Torr/100 μ in femur muscle. 3. The frequency distribution of tissuepO2 shows peaks far below venous oxygen pressure indicating longer diffusion paths than in vertebrate tissues. 4. In undiluted haemolymph theP 50 of the haemocyanin is 3 Torr at 25°C and pH 8.14. Cell-free haemolyph samples drawn from the heart and femur had an average pH of 8.08 and 8.09, respectively, at 22°C. Under these conditions the haemocyanin is completely saturated in the arterial blood, and 88% saturated in venous blood. 5. The haemocyanin ofEurypelma shows a strong Bohr effect (ΔlogP 50/ΔpH=−0.52 between pH 7.27 and 8.24, and −1.2 at haemolymph pH).